ol-ext/particule/Rain.js

A set of cool extensions for OpenLayers (ol) in node modules structure

/*
  Copyright (c) 2020 Jean-Marc VIGLINO,
  released under the CeCILL-B license (French BSD license)
  (http://www.cecill.info/licences/Licence_CeCILL-B_V1-en.txt).
*/
import ol_ext_inherits from '../util/ext'
import ol_particule_Base from './Base'

/** Rain particules to display clouds over the map
 * @constructor
 * @extends {ol_particule_Base}
 * @param {*} options
 *  @param {ol.Overlay} options.overlay
 *  @param {ol.pixel} coordinate the position of the particule
 */
var ol_particule_Rain = function(options) {
  if (!options) options = {};
  
  ol_particule_Base.call(this, options);

  this.z = Math.floor(Math.random()*5) + 1;

  var canvas = document.createElement('CANVAS');
  canvas.width = 50;
  canvas.height = 50;
  var ctx = canvas.getContext('2d');
  this.gradient = ctx.createRadialGradient(0,0, 0, 0,0, 25);
  this.gradient.addColorStop(0, 'rgba(0,0,80,0)');
  this.gradient.addColorStop(1, 'rgba(0,0,80,.3)');

};
ol_ext_inherits(ol_particule_Rain, ol_particule_Base);

/** Draw the particule
 * @param {CanvasRenderingContext2D } ctx
 */
ol_particule_Rain.prototype.draw = function(ctx) {
  ctx.save();
    var angle = this.getOverlay().get('angle');
    ctx.beginPath();
    var x1 = Math.cos(angle) * 10 * (1+this.z/2);
    var y1 = Math.sin(angle) * 10 * (1+this.z/2);
    ctx.lineWidth = Math.round(this.z/2);
    ctx.strokeStyle = this.gradient;
    ctx.translate (this.coordinate[0], this.coordinate[1]);
    ctx.moveTo(0,0);
    ctx.lineTo(x1, y1);
    ctx.stroke();
  ctx.restore();
};

/** Update the particule
 * @param {number} dt timelapes since last call
 */
ol_particule_Rain.prototype.update = function(dt) {
  var dl = this.getOverlay().get('speed') * dt / this.getOverlay()._fps * this.z;
  var angle = this.getOverlay().get('angle');
  this.coordinate[0] += dl * Math.cos(angle);
  this.coordinate[1] += dl * Math.sin(angle);
};

export default ol_particule_Rain